Nov. 6,1916 
Grain of the Tobacco Leaf 
279 
after fermentation and these were dehydrated in absolute alcohol, cleared 
in xylol, and mounted in Canada balsam. 1 
In ordinary transmitted light the samples showed no marked varia¬ 
tions one from the other. The use of polarized light, however, revealed 
striking differences in the degree to which the grain substance had 
become aggregated, and it was found that these differences seemed to 
remain fairly constant between the good-burning samples on the one 
hand and the poor-burning samples on the other. In order that the 
condition found might be expressed in some form more concise than by 
descriptive terms, a system of scoring the degree of aggregation was 
adopted. By using a maximum perfect score of 10 points, convenient 
minor classes occurred as follows: “Good,” 8 points; “fair,” 6 points; 
“poor,” 4 points; and “very poor,” 2 points. A detailed score (Table 
II) of a poor-burning sample will best serve to illustrate the method 
used. 
Table II .—Detailed score of poor-burning sample from Plot I, Red Lion, Pa,, 1913 
Disk No. 
Grain. 
Score. 
1 
2 
3 
4 
5 
6 
7 
8 
9 
Poor aggregation; small amount; haze of single and cryptocrys¬ 
talline crystals. 
Poor aggregation; small aggregates; flaky spherites, cryptocrys¬ 
talline haze. 
Very poor aggregation; small amount; fine cryptocrystalline 
haze with larger singles. 
Very poor aggregation; dense, hazy mass. 
Poor aggregation; similar to disk 4, though less dense. 
No aggregation; spherites and cryptocrystalline haze.. 
Very poor aggregation; similar to disk 4. 
No aggregation; fine, thin cryptocrystalline haze. 
Poor aggregation; dense; a few flaky and a few black superficial 
aggregates.. 
4 
3 
2 
2 
3 
1 
2 
o- 5 
2. o 
i9- 5 
Divided by 9, score is 
2.16 
It will be noted in the score that the word “spherites” is used in the 
description of some of the samples. These are of much more frequent 
1 Of the 1913 material only the two best and the two poorest-burning samples were studied in detail, 
while the samples from all the fertilizer treatments used in 1914 were subjected to an equally thorough 
investigation. The microscopical data here presented represent, for the 1913 material, detailed exami¬ 
nations of disks cut from each of 18 representative leaves from each of the four fertilizer treatments 
after the fermentation process was completed. In 1914 , however, the leaves were selected in the field 
before the plants were harvested. In this case three leaves from each of six average plants in each treat¬ 
ment were sampled in the field by removing a small disk of tissue from each leaf selected at a point equi¬ 
distant from the midrib and the margin and midway between the base and apex. These disks were 
killed in absolute alcohol and preserved for future study in the same liquid. The leaves thus sampled 
were the eleventh, twelfth, and thirteenth below the point of topping, which point in all of the plants bore, 
as nearly as possible, the same relation to the developing flowers. These same leaves, having been tagged 
in the field, were used later in a preliminary study of the development of the grain and, after fermenta¬ 
tion, for determining the character of the fully developed grain together with the fire-holding capacity and 
certain chemical analyses. 
